Piezoelectric cleaning device with removable workpiece



E1. BURT 'July 7, 1970 PIEZOELECTR'IC QLEANING DEVICE WITH REMOVABLE WORKPIECE Filed Jan. 50, 1963 I!fflflllillflllllflff? E LE CTRIC OSCILLATOR W A TE R S 0 U R C E T R U s R Y m .V m N L R E 0 ww w A A M E United States Patent 3,518,766 PIEZOELECTRIC CLEANING DEVICE WITH REMOVABLE WORKPIECE Emanuel Burt, 2714 SW. 36th Ave., Miami, Fla. 33135 Filed Jan. 30, 1969, Ser. No 795,239 Int. Cl. A61c 3/06 US. Cl. 3258 6 Claims ABSTRACT OF THE DISCLOSURE A piezoelectric dental cleaning device comprising a tubular piezoelectric crystal centrally supported within a handle-like hollow casing with a seal near the lower end of the crystal, a removable and replaceable working tip having a working end mechanically coupled at the upper end of said crystal to form a compound resonator therewith, means for effecting longitudinal ultrasonic vibration of said crystal and means for delivering coolant through said crystal and directing it outwardly along the tip to a region adjacent the working end of the tip to flush debris loosened by ultrasonic vibration of said working end of said tip.

RELATED APPLICATION A related application Ser. No. 558,028 of Seymour Robinson is co-pending.

This invention relates to a cleaning device utilizing ultrasonic vibrations for dislodging debris, for example, from a tooth, including tartar, stain, loose particles, calculi, etc.

In general, apparatus embodying the principles of the invention comprises a removable and replaceable tip mounted in a hand piece, the tip being mechanically coupled to a piezoelectric crystal in such a 'way so as to form with it a compound ultrasonic resonator. The vibratory action of the crystal is transmitted to the tip by novel mechanical coupling which permits ready removal and replacement of said tip as desired. The crystal as so formed as to provide longitudinal ultrasonic vibrations when it is activated by high frequency electrical impulses and the resultant ultrasonic vibrations are transmitted by means of the novel coupling directly without reverberatory vibrations through the tip to the point of use. The crystal utilized is of tubular configuration made preferably of lead zirconate and/or lead-titanate ceramic material which is so formed that it has the quality of expanding and contracting longitudinally at ultrasonic frequencies and is joined removably end to end to the tip by the novel coupling means so that the ultrasonic tip movements are directly related to the longitudinal expansion and contraction of the activated crystal. While the latter may be designed to be operated at frequencies from 20,000 c.p.s. upwards to 45,000 c.p.s., for dental applications, such frequencies usually will not exceed 35,000 c.p.s. Since each crystal must be designed for a required frequency, the crystal and tip coupled thereto constitute 1 a matched pair and form said compound resonator. Provision is made in the hand piece for supporting and retaining the crystal and coupling for the tip. In addition, a water duct in conjunction with the hand piece and tip is provided for coolingthe crystal as 'well as ejecting a stream of water adjacent the tip during use.

Use of magneto-strictive activation of responsive metal alloys to provide ultrasonic vibrational motion of a cleansing tip is known in the art. However, a major difiiculty in prior art devices is the concurrent production of reverberatory vibrations during use that may produce undesirable effects.

In the foregoing related Robinson application, the

3,518,766 Patented July 7, 1970 working tip and crystal are permanently joined together so that different working conditions requiring different tips entailed is need for a plurality of complete tools. This need is eliminated in the present invention by providing for replacement of the tip as required without undesirable reverberatory vibrations.

Principal objects and features of this invention are, therefore, the provision of a simply constructed light weight ultrasonic cleaning device having particular adaptability for dental use utilizing ultrasonic vibrations of a removable and replaceable cleaning tip which are generated in such a way that they are directly transmitted to the said removable and replaceable tip without any undesirable reverberatory vibrations.

Other objects and features of the invention are the ice provision of a mechanically simple and effective ultrasonic cleaning device utilizing a compound resonator including a tip and a piezoelectric crystal as the source of ultrasonic vibrations that may be manufactured relatively inexpensively and which will be trouble free and long-lasting in operation and free of reverberatory vibrations.

Other objects and features of the invention are to provide a novel manner of providing debris flushing water at the work tip.

Still other objects and features of the invention are to provide a simple system of cooling the crystal transducer and of conveying the coolant to the work tip for flushing purposes.

Further objects and features of the invention will become apparent from the following specification and the accompanying drawings, wherein:

FIG. 1 is a longitudinal sectional view of a device embodying the invention;

FIG. 2 is a section taken along line 2-2 of FIG. 1;

FIG. 2a is a similar section of a modified construction;

FIG. 3 is an end view seen from the plane of line 33 of FIG. 1; and

FIG. 4 is a sectional view of an end plug-in cap for conducting coolant to the device of FIG. 1 as well as electric current to the crystal transducer.

Referring now to the drawings, and in particular FIG.

1, the reference character 10 denotes generally a cleaning device including an outer insulated casing 11 in the form of a tubular hand piece for convenient manipulation by an operator. This casing 11 may be of plastic or any other suitable electrical insulating material and includes a head end 12 'which is externally threaded at 13 and provided internally with a passageway 14 of narrower internal diameter. The opposite or base end of the hand piece is internally threaded at 15 for purposes presently to be described.

A tubular piezoelectric crystal transducer 16 is mounted internally of the hand piece 11. In the embodiment shown, this crystal comprises a lead zirconate-lead titanate ceramic crystal of tubular shape formed so as to be capable of ultrasonic vibrational activity in its longitudinal direction when activated by high frequency electrical impulses delivered to it as will be described. This crystal transducer 16 is of smaller diameter than the internal diameter of hand piece 11 and is supported coaxially with said hand piece preferably as follows:

A metallic tubular insert 17 preferably of stainless steel or like non-corrosive metal having a diameter approximating the internal diameter of crystal transducer 16 is provided. This insert 17 has an annular external collar 18 disposed in its length and the forward end of said insert is positioned with the base (in this instance left end) of said crystal transducer 16 until said collar abuts the base end of said crystal transducer. The said forward end of said insert is permanently secured to the crystal transducer 16 as by epoxy cement at 19. A nonconductive water tube 20 as of silicone rubber is mounted permanently on the rearward portion of metallic insert 17 with its forward end abutting the rearward face of annnular collar 18 thereof.

Electrical connection to the crystal transducer 16 is effected by providing coatings 21 and 22 of silver or other conductive metal respectivel internally and externally of the crystal transducer 16 which are fused thereto. These coatings are approximately 0.0 015 inch thick and extend to about 38 inches of the inner end and A inch of the outer wall of said crystal transducer 16. They may be applied by electrodeposition or in any other conventional way. Flexible leads 23 and 24 in respective conductive contacts with said coatings 21 and 22 are permanently connected thereto respectively by suitable conductive epoxy cement and are respectively connected as by soldering to a pair of connector prongs or pins 26, 27

mounted in spaced-apart insulative condition to project outwardly of a rear end hand piece cap 28 preferably of the same material as said hand piece 11 and applied at the rear or base end of said hand piece.

This cap 28 has an externally threaded portion 29 that may be screwed into the threaded portion at the base end of said hand piece. The maximum diameter of the cap 28 behind its threaded portion 29 is substantially the same as the outer diameter of said hand piece 11 so that when it is screwed into the latter the rear end of the assembly of cap and hand piece are flush and present unbroken continuity for purposes to be described.

The cap 28 also has a receiving hole 30 extending in its axial direction into which the rearward end of Water tube is mounted preferably with a leak-proof press fit, and includes an O-ring 30' of silicone rubber for seal purposes.

The assembly of cap 28 with water tube 20, metallic insert 17, crystal transducer 16 and leads 23 and 24 is adapted to be mounted within said hand piece 11 from its rearward end. Prior, however, to such installation into said hand piece 11, a potting coating 31 of a suitable insulative molding compound such as silicone rubber is applied over the rearward external surface of the crystal transducer 16, over the metal insert 17 and over the flexible leads 23, 24 as well as the exposed surface of the water tube 20. This coating 31 when it sets serves to secure the rearward or base end of said crystal transducer 16 securely in position on cap 28 and when the latter is then screwed onto the rearward threaded end of said hand piece provides a resilient end support for the rearward end of said crystal transducer 16, to insure its proper vibratory activity when excited electrically as will be described. Without this support and clamping action by said potting component inefficient vibratory activities will occur at the work piece 31 which is mounted at the other end of said crystal transducer as will now be described.

This workpiece 31 is preferably of metal, e.g. stainless steel or beryllium copper or other suitable material in the form of an elongated rod portion 32 terminating in an appropriately shaped working tip 33 adapted for particular ultrasonic dental tooling operations. Since this tip may vary in specific shape as required, it is essential that the workpiece of which it is part be removable and replaceable on the crystal transducer 16 as required. Specifically novel coupling and mounting means between the forward or outer end of crystal transducer 16 and the workpiece 31 are required to provide efficient transmission of the longitudinal vibrations of the electrically excited crystal transducer 16 without reverberatory vibrations so that said workpiece 31 and crystal transducer become in fact a compound resonator in order to provide efficient dental tooling action by the specific working tip 33 of said workpiece 31.

To this end, the novel coupling means between the crystal transducer 16 and the workpiece 31 comprises a tubular metallic impedance transformer 34 of stainless steel or other suitable metal. The inner tubular portion 35 of this transformer 34 has approximately the internal diameter of the outward or forward end of said tubular crystal transducer 16 and is inserted into the latter to the limit permitted by the annular shoulder 36- and rigidly and permanently secured to the crystal transducer as by an epoxy cement 37. The annular shoulder 36 has substantially the same diameter as the external diameter of said crystal transducer 16 and its peripheral surface projects forwardly for a portion of the length of said transformer and then tapers inwardly to provide a bevelled annular shoulder surface 38 and terminates in a cylindrical straight walled tubular portion 39 of somewhat larger external diameter than the inner tubular portion 35.

The central axial hole 40 of the metallic transformer 34 extends through the length of the latter and communicates with the inner hollow space 41 of said crystal transducer 16.

The inner end 42 of the workpiece 31 is removably and replaceably insertable as by a press fit into the forward end of the axial hole 40* of transformer 34. When so mounted, the workpiece extends outwardly coaxially and forwarding of tubular crystal transducer 16.

A hollow, removable forward screw cap 43 of metal or rigid plastic material with internally threaded end 44 is removably screwable onto the threaded end 13 of hand piece 11. This screw cap 43 has a hollow portion 45 of larger internal diameter than the maximum diameters of the crystal transducer 16 and its attached transformer 35. It also is provided internally with a tapered shoulder 46 adjacent to but spaced from the tapered or bevelled surface 38 of said transformer and a forward hollow tubular portion 47, the diameter of whose hole 48 is of substantially larger diameter than that of the body of workpiece 32 which extends through and outwardly thereof without making contact anywhere therewith.

An O-ring 49 of rubber or other resilient material located internally of cap 43 between its tapered shoulder 46 and bevelled shoulder surface 38, serves when cap 43 is screwed into place to maintain the forward end of crystal transducer 16 as well as the body of workpiece 32 axially centered and aligned and free of all contact with internal surfaces of hand piece 11 or cap 43 and also to provide back pressure against the resilient potting coating 31'.

The cleaning device 10 thus far described is connected to a source of water supply as well as oscillatory electric power supply through a removable plug in end fitting 50 (FIG. 4). This fitting 50 comprises a tubular body 51 that may be mounted over the rearward cap 28 and rearward portion of hand piece 11 with a slide fit. It includes a water plug conduit 52 connected to a source of water supply 53 which fits into the rear end of water tube 20 and electrical sockets 54 (only one of which is shown) into which the plugs 26 and 27 extend when the end fitting is mounted on the hand piece 11. These sockets 54 are connected to a conventional oscillator 55 whose output'and frequency may be varied as desired. The oscillating power delivered from oscillator 55 will provide the desired piezoelectric effect and ultrasonic vibrations of said crystal transducer 16 and workpiece 32. For example, at an operating frequency of about 2 8,900 c.p.s., the applied voltage to the crystal transducer would be in the range of about 53 to 200 volts (RR) 40 watts at desired voltage. Conduit 23 and the inner wall of the crystal transducer 16 are preferably connected to the hot side of the oscillator 55 and conduit 22 and outer wall of transducer 16 to the neutral side for protection against possible shock.

To provide for a water outlet and to direct a pressure jet stream of water to the tip 33 of the workpiece 31 adjacent the region of the dental surface being worked upon for removal of debris thereat by such stream, the

workpiece is provided either with a longitudinally extending narrow slot or groove 56 or is of hollow extruded stainless steel whose lumen 56' is approximately .024" in diameter. The respective inner ends of the slot, groove or lumen communicate via hole 40 with the inner space 41 of crystal transducer 16 and the respective outer ends terminate in proximity to the work tip 33 of said workpiece 31. This narrow slot or groove or lumen provides a restricted outlet for water or other coolant fed from the water source to water tube 20 and the interior space 41 of said crystal transducer 16 and ejection of this water as a pressure stream or jet adjacent the dental surface being treated 'by the tip 33 thus providing circulation of water or other coolant longitudinally through the crystal transducer 16 to cool the latter during operation and provides a flushing pressure jet stream for debris at the worktip 33.

In operation, the appropriate workpiece 31 is press fitted into place, cap 43 tightened and fitting 50 applied to the rear end of the hand piece 11, thus connecting water from source 53 and oscillatory current from oscillator 55 to the crystal transducer 16. This creates ultrasonic vibrations in said transducer 16 which, via the metallic transformer 34, are transmitted directly to the workpiece 31 and its tip 33 so that the latter also has ultrasom'c vibrations created in it so that when it is ap plied to a tooth or other dental surface to be cleaned these vibrations serve to liberate accumulated dirt on such surfaces which are flushed away as debris by the jet water spray delivered via slot or groove 56.

The crystal transducer 16 of tubular form consist of a lead zirconate-lead titanate ceramic having the unique quality of expanding and contracting in longitudinal direction when excited by high frequency electrical oscillations as described. While such crystals may be designed to produce this effect with oscillations at from 20,000 c.-p.s. to 45,000 c.p.s., preferably, for dental application, the response will not exceed 35,000 cps. Each crystal 16 is designed to respond more or less to a specific frequency and the replaceable workpiece 31 coupled thereto removably as described provide matched pairs providing Crystal 1 C1ystal2 (strontium (niobium additive) additive) u lin coeflicients:

C 1%1u? 59 64 66 70 Kn 34 35 Piezoelectric Constants:

D 3 (meters per volt) 284X- 375x10- D3 (meters per volt) -120 l0 -170 10- Gas (volt-meters per Newton) 25 10- 24x10- G31 (volt-meters per Newton) 1l 10- --11.5 10-= Dielectric Constant,Ka 1, 300 1, 700 Frequency Constants:

Radial (cycle-meters per second) 2, 100 2, 000 Thickness (cyelemeters per seeon 1, 950 1, 800 Elastic Constants:

YEn (gIIL/OIII. 8.2)(10- 6.1)(10' YEas (gm./cm. 6.6)(10 53 x10- Density (gm./cm. 7.6 7. 6 Mechanical Q, 600 65 Curie Point 0.). 325 365 Crystal 16 can be electrically energized to have vivratory components in other than longitudinal directions to provide various mechanical effects at the tip as desired. This would be accomplished by changing the excitation frequency. In addition, the location of applying the voltage to the crystal can be utilized to produce different effects. For example, by applying the voltage across opposite ends of the crystal produces a torsional effect. Another factor of crystal operation is the relative extent of crystal surface coverage by the silver coating. By fiattening the tip and making the width and thickness of the tip approximately equal one can achieve lateral movement of the outer tip end and consequently the pattern of tip movement can be altered by adjustment of the tip design if other than pure longitudinal or axial motion of the tip is desired.

While specific embodiments have been disclosed, variations within the scope of the present disclosure may be possible within the skill of the art. There is no intention of limitation to the exact disclosure or abstract herein presented.

What is claimed is:

1. A piezoelectric dental cleaning device comprising a tubular hand piece having head and base ends, a tubular piezoelectric crystal transducer, a removable head cap for the head end of said hand piece, a removable base cap for the base end of said hand piece, a tubular insert secured permanently to a rearward end of said tubular crystal transducer, liquid conduit means secured at one end to said tubular insert and at its other end in said base cap, electric conduits joined electrically to inner and outer surfaces of said tubular crystal transducer, connectors extending outwardly of said base cap and electrically connected to respective of said conduits, resilient potting coating covering the rearward end of said transducer, the tubular insert, said liquid conduit means and said electric conduits to support said rearward end of said transducer resiliently in said hand piece when the base cap is mounted thereon, coupling means comprising a tubular metallic transformer secured permanently at the opposite end of said crystal transducer, a metallic workpiece mounted with a press fit into said transformer, and projecting through said head cap, said head cap and said transformer having corresponding tapered surfaces, resilient ring-like means positioned between said corresponding tapered surfaces of said transformer and said removable head cap to center said opposite end of said crystal transducer in said headpiece and maintain said workpiece free of contact with said head cap, said work-piece having a longitudinally extending conduit communicating at one end with the inner hollow space of said crystal transducer and terminating at its other end in proximity to a working tip of said workpiece, and means mountable over the base end of said handpiece for coupling a source of coolant for transit through the hollow space of said transducer to cool the latter and outwardly thereof as a jet via said other end of said longitudinally extending conduit, and means in said lastnamed means to connect said electric conduits to a source of oscillating electric current.

2. A piezoelectric dental cleaning tool according to claim 1, wherein said tubular metallic transformer has a portion dimensioned to fit into said opposite end of said transducer and to be"'secured permanently thereto, an annular external collar abutting said end, an inwardly tapered portion beyond said collar portion providing one of said tapered surfaces and a cylindrical tubular portion beyond the tapered portion into which latter tubular portion said workpiece is removably mountable with said press fit, and said head cap has an internal tapered shoulder providing the other of said tapered surfaces.

3. A piezoelectric dental cleaning tool according to claim 1, wherein said first mentioned tubular insert includes a portion mounted into said rearward end of said tubular crystal transducer, an annular shoulder portion abutting said rearward end and a second portion lying outwardly of said annular shoulder portion, said liquid conduit means having one of its ends mounted on said latter portion and its other end mounted in an opening in said base cap.

4. A piezoelectric dental cleaning tool according to said prongs to said source of oscillating electric current.

5. A piezoelectric dental cleaning tool according to claim 1, wherein said means mountable over the bas e end of said handpiece includes a water plug conduit couplable with said water conduit and connected to said coolant 9 source.

6. A piezoelectric cleaning device according to claim 1, wherein said piezoelectric crystal transducer is comprised of at least one of the group of materials consisting of lead zirconate and lead titanate ceramic crystals dirnentioned to provide longitudinal ultrasonic vibrations at frequencies ranging from about 20,000 to 45,000 c.p.s.

References Cited UNITED STATES PATENTS 3,213,537 10/1965 Baiamuth et a1. 32-28 3,368,280 2/1968 Friedman et a1. 32-58 3,427,480 2/1969 Robinson 310-8.1

ROBERT PESHOCK, Primary Examiner US. Cl. X. R. BIO-8.1 

